Personally, I find it hard to classify something as a zombie if it isn't dead. The original "zombi" was a dead person whose soul was stolen by a necromancer, thus making them a slave to the necromancer for eternity. The lore got altered, but the "zombi" was and will always be dead. 28 Days Later "zombies" are just "infected", since they're not dead at all. L4D "zombies" are also "infected". I Am Legend "zombies" are just crazy vampires. If anything, "infected" should just be considered mutants or something, as opposed to "undead". It's like calling a zombie a burrito after watching a few movies where all of the zombies were actually burritos. Don't make no sense.